The present invention relates to heat containment apparatuses suited for use in high temperature operations of substrates, such as brazing of drill bits.
The manufacturing of many downhole tools includes applying a wear-resistant coating (e.g., a hardfacing on a cutting structure), attaching cutting structures (e.g., a braze to attach a cutter), and/or attaching wear-resistant elements to protect the surface of the downhole tool from wear and abrasion. The application of these coatings requires the surface of the downhole tool (or component thereof) be at elevated temperatures, e.g., 650° C.-760° C. (1200° F.-1400° F.) for brazing. The elevated temperature may, at least in part, assist with reducing residual moisture on a surface and mitigate differential thermal expansion of two or more components.
To achieve this the downhole tool is heated in a kiln, or similar apparatus, then removed to apply the coating. In order to keep the surface at an elevated temperature after removal from the kiln, workers wrap the downhole tool with a ceramic blanket (or wrap or tape). Then, as the ceramic blanket is carefully peeled away to ensure that no particulates remain on the surface, the coating is applied. If during this process the surface cools below a certain threshold, e.g., about 480° C. (900° F.) for brazing, the downhole tool must be reheated and rewrapped before the process can continue.
With this process, defects and potential failure points can manifest in several places. First, when wrapping the heated substrate, ceramic particulates and fibers from the wrapper can become fused to the surface of the tool. Particulates and fibers that are not removed can create surface areas where the coating may fail to properly adhere to the tool surface. Thus, ensuring the surface is clean for coating is often time consuming, thereby increasing the chances of needing to reheat and begin again. The reheating and continuation of coating can further create defects or points of potential failure where the first coating and second coating interface.
Additionally, this process requires workers to handle materials at extremely high temperatures. Further, many of the processes performed produce harmful air borne chemicals and particulates. While workers employ safety measures (such as, insulated gloves and coveralls and respiratory devices), an apparatus that reduces defects and potential failure points in the downhole tools while further reducing worker safety risk would be of benefit to one skilled in the art.